# Redundancy and Modbus Connection Issues **URL:** \ **Category:** Ignition\ **Tags:** redundancy, ignition81\ **Created:** [May 2, 2023, 5:49am UTC](https://forum.inductiveautomation.com/t/redundancy-and-modbus-connection-issues/73128 "2023-05-02T05:49:01Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![joshdunstan](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/joshdunstan/32/43306_2.png) [@joshdunstan](https://forum.inductiveautomation.com/u/joshdunstan)\ **Post date:** [May 2, 2023, 5:49am UTC](https://forum.inductiveautomation.com/t/redundancy-and-modbus-connection-issues/73128/1 "2023-05-02T05:49:01Z")
Running Ignition 8.1.25 with redundancy enabled. Both servers are headless linux. Redundancy is cold & partial. I have a myriad of devices connected (~60), most are modbus, with a half dozen DNP3. When I perform a failover, the backup server does not successfully connect to any devices. The connected devices list would indicate they are connected, but inspecting the connections device side, there are no packets being sent (modbus) or packets slow to a crawl at 1 in 5sec (DNP3), which without history is as good as disconnected anyway and the data turns stale/bad. The log on the backup is filled with SocketIODelegate faults, for example: > java.io.IOException: End of stream reached. > at com.inductiveautomation.iosession.socket.AsyncSocketIOSession.run(AsyncSocketIOSession.java:74) > at java.base/java.lang.Thread.run(Unknown Source) ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/9/d/9d90e7acd4332c43a35d7cb976cd0bab8df1ff3c.png) I try reset the connection from the device end, but Ignition never re-initiates. The "End of stream" tells me that this is a modbus device closing the connection, which indicates in turn that the primary never let go of it completely? Backup server pre-fail over: ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/5/3/5309b5c7673068032f027fef10668ac5662deec0.png) Backup server post-fail over ![image](https://us1.discourse-cdn.com/inductiveautomation/original/3X/e/6/e60dcf8228266da59c786450aefa55dffb2e32c2.png) In opposition to the above, the device side of those modbus connections indicates disconnected and no packets are being sent. The tag browser also indicates bad data. Edit: I should add.. if I fail 'back' and assume control on the primary.. all of the connections resume and everything is ok! ---
**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\ **Post date:** [May 2, 2023, 12:26pm UTC](https://forum.inductiveautomation.com/t/redundancy-and-modbus-connection-issues/73128/2 "2023-05-02T12:26:23Z")
Hmmm. I can't help you with the IA driver (and I suspect you need to call support), but I'd be curious what you get if you substitute [my alternate driver](https://inductiveautomation.com/moduleshowcase/module/automation-professionals-llc-advanced-modbus). Perhaps in parallel with some extra tags to not disturb your production kit. It's a totally different code base, so if mine does the same, it probably isn't a problem inside Ignition. ---
**Author:** ![michel\_feria](https://avatars.discourse-cdn.com/v4/letter/m/ad7895/32.png) [@michel\_feria](https://forum.inductiveautomation.com/u/michel_feria)\ **Post date:** [August 7, 2024, 3:52pm UTC](https://forum.inductiveautomation.com/t/redundancy-and-modbus-connection-issues/73128/3 "2024-08-07T15:52:34Z")
Hello, I'm having a similar issue, I have 9 modbus TCP devices connected to a Master - backup redundancy pair. When the Master fails then the backup have access to all the devices, no problem with that but... when the Master comeback then 3 of 9 devices remains disconnected in the master but still connected on the backup server!!! Then I need to disable and enable the device again to hook the device to the master server... Any idea how to fix this? thanks in advance! MF ---
**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\ **Post date:** [August 7, 2024, 4:02pm UTC](https://forum.inductiveautomation.com/t/redundancy-and-modbus-connection-issues/73128/4 "2024-08-07T16:02:00Z")
> [@michel\_feria](#): > > Any idea how to fix this? Have you tried my alternate driver? It has settings specifically for situations like this. ---
**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\ **Post date:** [August 7, 2024, 4:10pm UTC](https://forum.inductiveautomation.com/t/redundancy-and-modbus-connection-issues/73128/5 "2024-08-07T16:10:28Z")
Make sure the "Standby Activity Level" is set to Cold. ---
**Author:** ![michel\_feria](https://avatars.discourse-cdn.com/v4/letter/m/ad7895/32.png) [@michel\_feria](https://forum.inductiveautomation.com/u/michel_feria)\ **Post date:** [August 7, 2024, 5:04pm UTC](https://forum.inductiveautomation.com/t/redundancy-and-modbus-connection-issues/73128/6 "2024-08-07T17:04:07Z")
I'm using Warm!! is that an issue? why Warm is not usable? thanks ! ---
**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\ **Post date:** [August 7, 2024, 5:04pm UTC](https://forum.inductiveautomation.com/t/redundancy-and-modbus-connection-issues/73128/7 "2024-08-07T17:04:48Z")
In Warm mode, devices are expected to make and keep connections on both master and backup. Sounds like you don't want that. ---
**Author:** ![michel\_feria](https://avatars.discourse-cdn.com/v4/letter/m/ad7895/32.png) [@michel\_feria](https://forum.inductiveautomation.com/u/michel_feria)\ **Post date:** [August 7, 2024, 5:04pm UTC](https://forum.inductiveautomation.com/t/redundancy-and-modbus-connection-issues/73128/8 "2024-08-07T17:04:59Z")
where can I find it? thanks ---
**Author:** ![pturmel](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/pturmel/32/3295_2.png) [@pturmel](https://forum.inductiveautomation.com/u/pturmel)\ **Post date:** [August 7, 2024, 6:44pm UTC](https://forum.inductiveautomation.com/t/redundancy-and-modbus-connection-issues/73128/9 "2024-08-07T18:44:00Z")
It is linked above, in comment #2. Here's another copy: > **[Ignition Third-Party Module Showcase](https://inductiveautomation.com/moduleshowcase/module/automation-professionals-llc-advanced-modbus)** > > Easily extend Ignition's core functionality with Third-Party Modules. The Module Showcase is a great place to find a solution that best meets your needs. ---
**Author:** ![michel\_feria](https://avatars.discourse-cdn.com/v4/letter/m/ad7895/32.png) [@michel\_feria](https://forum.inductiveautomation.com/u/michel_feria)\ **Post date:** [August 7, 2024, 6:46pm UTC](https://forum.inductiveautomation.com/t/redundancy-and-modbus-connection-issues/73128/10 "2024-08-07T18:46:21Z")
Hi Kevin, I need a fast switchover from Mater to backup and vice versa. That's why I selected warm instead of cold mode. but why isn't working in warm mode? why the other 6 devices seem to be ok with the warm mode but only 3 are not working? ---
**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\ **Post date:** [August 7, 2024, 7:14pm UTC](https://forum.inductiveautomation.com/t/redundancy-and-modbus-connection-issues/73128/11 "2024-08-07T19:14:26Z")
It sounds like these devices limited in the number of connections they can accept/maintain. ---
**Author:** ![michel\_feria](https://avatars.discourse-cdn.com/v4/letter/m/ad7895/32.png) [@michel\_feria](https://forum.inductiveautomation.com/u/michel_feria)\ **Post date:** [August 7, 2024, 7:39pm UTC](https://forum.inductiveautomation.com/t/redundancy-and-modbus-connection-issues/73128/12 "2024-08-07T19:39:03Z")
good point, thanks very much for your help! I've a last question, how faster is Warm vs Cold mode? I mean, practically is very different? thanks again! ---
**Author:** ![Kevin.Herron](https://sea1.discourse-cdn.com/inductiveautomation/user_avatar/forum.inductiveautomation.com/kevin.herron/32/7259_2.png) [@Kevin.Herron](https://forum.inductiveautomation.com/u/Kevin.Herron)\ **Post date:** [August 7, 2024, 7:42pm UTC](https://forum.inductiveautomation.com/t/redundancy-and-modbus-connection-issues/73128/13 "2024-08-07T19:42:06Z")
I don't know, you'll have to try it and see. Ignition failover in any configuration isn't very fast, so I wouldn't expect much difference, but 🤷‍♂️